html,
body {
    width: 100vw;
    height: 100vh;
    padding: 0;
    margin: 0;
}

#canvas {
    width: 100%;
    height: 100%;
    background: #fff0;
    display: block;
}

body::after {
    content: 'Canvas 画板';
    display: flex;
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    /* background: #abf; */
    background: #e3e3e3;
    font-size: 85px;
    justify-content: center;
    align-items: center;
    color: #d3d3d3;
}
